Double Circular-triangular Six-degrees-of-freedom Parallel Robot

This paper describes a new structure of a six-DOF parallel robot. First, a known planar three-DOF double-triangular structure is modified by replacing the stationary triangle with a circle. It increases the work envelope considerably especially when rotational motions are required. The ability for unlimited rotational motion allows extending the structure into six-DOF by using two sets of stationary circles and moveable triangles. Each set can actuate the moving triangle in a planar three-DOF motion and hence actuate a line connecting the centers of the movable triangles in four-DOF. The robot's end-effector is attached to a link along this line while rotation about and translation along this line are obtained by the additional rotational DOF of the movable triangles. The solution of the direct kinematics of this six-DOF manipulator is given in a closed-form and it is shown that at most, four different solutions exist.